<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- 检测用户提交的内容中是否含有"autofocus"属性 -->
    <input onfocus="write(1)" autofocus />
    <input onblur="write(1)" autofocus>
    <input autofocus>
  </body>
</html>
